Diet, exercise, sleep, genetics and the environment are factors generally recognized as strongly influencing health. Sunlight as a detrimental environmental factor causing skin cancer and other conditions is often discussed. The beneficial effects of sunlight have had much less attention.
For many individuals moderate increases in ultraviolet sunlight exposure as in outdoor work, careful sunbathing or lamp exposure can provide benefits. The benefits include: decreased blood pressure, decreased resting heart rate, increased cardiac output, reduced blood cholesterol, increased liver glycogen stores, reduced blood sugar, increased muscular strength and endurance, increased resistance to infections, increased oxygen carrying capacity of the blood, increased adrenaline in tissues, increased stress tolerance, and increased hormones, Kime, 42.
The purpose of this invention is to provide methods and apparatus to increase the exposure of the skin when the exposure might be deficient such as during dark winter days and decrease the exposure when the exposure might be excessive such as during bright spring and summer days. The proper exposure of skin to solar radiation especially in a changing environment is important to promote health and reduce the risk of disease. An indoor deficiency in ultraviolet B (280 nm to 315 nm) is common. Excessive dietary vitamin D intake with associated problems results from attempts to compensate for the ultraviolet B exposure deficiency. Methods to increase the indoor ultraviolet B (UV-B) exposure, to avoid a deficiency in exposure and possible vitamin D deficiency while minimizing the risk of overexposure are included.
Irregular exposure such as excessive weekend and vacation sunlight exposure for persons working indoors during the week is a common problem. Irregular exposure is prevalent in developed countries and is a factor in the increasing incidence of the often fatal melanoma of the skin. Another purpose of this invention is to provide apparatus and methods to obtain a better balance in the day to day ultraviolet exposure of the skin.
Not enough sunlight and vitamin D deficiency can result in poor health and susceptibility to illness. Rickets in children, easy-to-break bones in the elderly, a possible increased susceptibility to some types of cancer, Ainsley, 9, and heart disease, Kime, 42, are typical conditions associated with insufficient UV-B sunlight exposure. The annual health care cost for fractures in the elderly is approximately 10 billion dollars in the U.S. alone, Avioli, 13. Scragg, 70, found coronary heart disease mortality may be associated with vitamin D deficiency (avoidable by sufficient UV-B exposure of the skin).
Sunlight exposure is beneficial for moderating hypertension, high blood sugar and many other conditions, Kime, 42. However, too much sunlight exposure increases the risk of skin cancer and DNA mutations. There is a need to adjust the skin exposure to avoid both insufficient exposure and excessive exposure. The best exposure for an individual varies with skin characteristics. The ratio between too much and too little exposure may be relatively small such as less than a factor of roughly three for face and arm exposure or relatively large such as a factor of 25 for whole body exposure.
Sunlight exposure is related to the important calcium balance. Modern populations have a low calcium diet presumed to result in increased osteoporosis, hypertension and colon cancer, Heaney, 38. The exposure to sunlight can increase the absorption of calcium in the intestine partially counteracting the effects of low amounts of calcium in the diet. Also, sunlight exposure is associated with increased bone mineralization, Kime, 42. Calcium, important in the functioning of cells, interacts strongly with vitamin D (and thus UV-B sunlight exposure), phosphorus, and magnesium. Too much calcium can result in urinary stones and interference with absorption of other essential minerals, Williams, 84. In infancy, excess vitamin D intake may result in hypercalcemia, Oppe, 61.
Vitamin D fortification of many foods is used in the U.S. for protection from rickets and other diseases for those with insufficient vitamin D generated in the skin by ultraviolet B exposure. However, the average person has an intake several times the recommended daily amount. As discussed by Kummerow, 45, and Fraser, 27, an increased mortality and incidence of vascular disease and other conditions may be resulting from high dietary intake of vitamin D. Linden, 49, found myocardial infarction patients had high intakes of vitamin D. Knox, 43, found increased ischemic heart disease mortality for those with high vitamin D intake and also for those with low calcium intake.
Fraser, 27, recommends obtaining the vitamin D from careful sun exposure rather than the diet. Along with obtaining proper exposure of the skin, the diet must be modified to avoid the excess dietary vitamin D intake to obtain the corresponding health benefits. Increased intake of fruits and vegetables tends to reduce intake of other foods with high vitamin D content due to fortification. Although vitamin D is needed primarily in the dark season in northern areas, the extensive fortification is present continuously during the year and is present in the foods for both northern and southern areas.
Historically, problems with insufficient exposure became common in the 1800's in higher latitude cities. With the start of the industrial revolution people moved from farms to cities. The narrow streets and smoke filled sky obscured the sunlight as shown by a photograph of a typical neighborhood, Goldsmith, 32. The incidence of rickets in children increased and this was later found to be due to insufficient ultraviolet B solar radiation exposure. The solar radiation UV-B was obscured both indoors and outdoors. Factory work rather than farm work greatly reduced sun exposure.
Those still involved in farm work tend to have good health for many conditions. The Gambia, is a West African, primarily agricultural country with both men and women cultivating the crops. There is significant outdoor exposure and a mainly vegetarian diet. This country has one of the lowest age standardized cancer incidences in the world. The incidence is more than five times lower than the incidence in the United States. In the U.S., a study in 1941 demonstrated states with a higher percentages of farmers had a trend for lower cancer mortality rates. States with a higher solar radiation index had an even stronger trend for lower cancer mortality, Apperly, 12.
The rickets problem was generally solved by the addition of vitamin D to milk and other foods. However, too much vitamin D may produce toxic effects such as hypercalcemia, Oppe, 61. Excessive vitamin D can be lethal and it is used as a rodenticide, Fraser, 27. Too much vitamin D can cause damage to the arteries. A typical desirable ratio of recommended maximum to recommended minimum dietary intake of vitamin D for infants is a factor of 2.5. Vitamin D generated in the skin by sunlight exposure has the advantage of only small amounts of vitamin D being released. The maximum accumulated amount of sunlight generated vitamin D in the skin is limited reducing the risk of toxic effects. In addition, the deleterious cholesterol in the skin and arterial plaque is reduced by sunlight exposure, Kime, 42. Cholesterol in the skin is converted to vitamin D and other compounds by exposure to UV-B radiation.
The narrow streets and smoke filled sky of the 1800's generally are no longer present. However, the common economic low-melting-temperature window glass blocks most of the ultraviolet B radiation. If one were to photograph the insides of homes and businesses with an ultraviolet B camera, most would be dark to dim just as were the homes and streets of the 1800's. Bare fluorescent lamps without diffuser covers brighten the inside some. Open windows and doors in the spring and fall can brighten the inside of homes in the UV-B just as the mood and spirit brightens in sunny weather. However, now, many homes and workplaces switch from heating to air conditioning with little or no opening of windows in the spring and fall. This leaves an indoor environment with incandescent lighting essentially continually dark in the ultraviolet B spectral region. Hospitals with windows that do not open and fluorescent lighting with prismatic plastic diffusers also are essentially continuously dark in the UV-B.
Those of the elderly who are inside all the time and who do not obtain vitamin D from the diet or supplements can become deficient in vitamin D and develop weak easy-to-break bones. Even in bright countries such as Kuwait, rickets occurs since children spend much of their time inside, Lubani, 51. Dark skinned persons migrating to higher latitudes can encounter vitamin D deficiency problems. Recently, rickets from vitamin D deficiency was reported by Brunvand, 17, for Pakistani children in Oslo, Norway. One approach would be to drink more vitamin D fortified milk to compensate for the lack of vitamin D generated by UV-B irradiation of the skin.
Another approach could be to increase the UV-B radiation indoors by using UV-B transmitting windows or appropriate fluorescent lamps, an object of this invention.
For those who spend significant time outdoors, overexposure can be a problem in the spring and summer on bright days. During this period bare tube fluorescent lamps, Maxwell, 56, open windows, or open doors can aggravate the overexposure problem during long exposure periods indoors. A method of this invention is to move ultraviolet B blocking diffusers over bare fluorescent tubes in the bright season to avoid a possible exacerbation of the overexposure problem.
In cold climates, many persons are deficient in ultraviolet and visible solar radiation exposure of the skin in the winter due to blocking of ultraviolet solar radiation by window glass. Also the clothing worn outdoors in the winter covers much of the skin greatly reducing the exposure. The short length of the day at high latitudes restricts the time available for sunlight exposure. In addition, the low sun angle at midday in the winter at high latitudes reduces the ambient solar irradiation due to the long path length through the atmosphere. These factors make it desirable for some persons to increase the exposure of the skin during the cold dark season. Leach, 46, found office workers in Bristol England receive less than an average of 0.7 mJ/sq. cm. per day of biologically effective radiation, a very low value, in the dark season from November through February, FIG. 1.
In hot climates the skin of many persons is excessively exposed to solar radiation. The long length of the summer day increases the time when solar radiation overexposure can occur. The high sun angle at midday in the summer increases the ambient solar irradiation due to the small amount of scattering and absorption in the short nearly vertical path length through the atmosphere. These factors make it desirable for some persons to decrease the exposure of the skin during the hot bright season.
The solar radiation in different spectral regions, UV-B, 280 to 315 nanometers, UV-A, 315 to 400 nanometers, visible light 400 to 700 nanometers and infrared radiation affect various health conditions. There are several suitable window materials such as ultraviolet transmitting glass or plastic with spectral transmission characteristics described by Driscoll, 23, and Sliney, 72. The increased cost of ultraviolet transmitting materials can be partially offset by using a small window orientated toward the sun for transmitting the solar radiation to a room frequently occupied such as a kitchen or living room.
The ultraviolet light rays, UV-B with a wavelength of 280 to 315 nanometers, are beneficial in the production of vitamin D in the skin. However, chronic exposure of untanned skin to ultraviolet solar radiation, especially UV-B, can be associated with DNA damage and an increased risk of skin cancer. Thus, care is needed to obtain adequate exposure in dark seasons and avoid excessive exposure in bright seasons. By reducing the bright season exposure more than the increase in the dark season exposure an increase in the risk of squamous cell skin cancer can be avoided, Lytle 53. By not chronically overexposing untanned skin an associated increase in the risk of melanoma skin cancer and other diseases can be avoided.
Vitamin D deficiency can be a problem for those confined indoors in nursing or other homes with insufficient ultraviolet exposure and a deficiency in dietary vitamin D. In some areas, especially far from the equator, there may not be sufficient sunlight for vitamin D generation in winter months. In addition to latitude, weather affects sunlight availability.
Dietary or tablet supplements are commonly used to avoid vitamin D deficiency. However, there may be problems associated with the use of dietary and tablet supplement vitamin D rather than solar radiation generated vitamin D. Large amounts of dietary or tablet supplement vitamin D can be ingested, however, vitamin D generated in the skin tends to self limit. Accumulated cholecalciferol blocks further synthesis of vitamin D in the skin, Heaney, 38. Fraser, 27, states: "Evidence from domestic animals suggests that persistent feeding of dietary vitamin D may be associated with the development of chronic vascular disease. For this reason alone it is prudent to advise that vitamin D should be obtained from the environment by careful exposure of the skin to solar ultraviolet light rather than from the artificial source of dietary supplements."